Magnetic needle steering systems and methods

A method for guiding passage of an implement through or within tissue of an animal body, the method comprising:

• inserting at least a portion of a steerable assembly into the animal body, the steerable assembly comprising an elongated body structure, an implement arranged at a distal end of the elongated body structure, and a premagnetized material or an electromagnet arranged closer to the distal end than to a proximal end of the elongated body structure;
• providing a magnetic resonance imaging system comprising at least one magnetic field source external to an animal body;
• and
• altering at least one of strength or position of the at least one magnetic field source to interact with the premagnetized material or the electromagnet to effectuate movement of the implement within the animal body.